Musnad Ahmad 435:36

Abu ‘Amr Marwan ibn Shuja’ al-Jazari narrated to us, he said: Khasif narrated to us, from Mujahid and ‘Ata’, from Ibn ‘Abbas, that Mu’awiyah informed him: That he saw the Messenger of Allah, may Allah bless him and grant him peace, "shorten some of his hair with a pair of shears." We said to Ibn ‘Abbas: "This has not reached us except from Mu’awiyah." He said: "Mu’awiyah was not accused regarding the Messenger of Allah, may Allah bless him and grant him peace."